Mechanical Gemstone Cleaning


The principal advantage of mechanical gemstone cleaning is getting beautiful results on difficult to clean set gems with minimal effort. Although there are home kits for cleaning jewelry with ultrasonic, steam, and boiling systems, these techniques are best left to the professionals (who hopefully have liability insurance to cover unfortunate outcomes).

The main risks to your jewelry with mechanical gemstone jewelry don’t come from the equipment but rather from the unique characteristics of your individual gems. Inclusions, undetected tiny fractures and structural stresses, and the chemical qualities of your gems and any treatments they’ve received, if not identified by a professional gemologist, could lead to poor, if not disastrous results if your gemstones are placed in the wrong kind of mechanical system.

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Inclusions, some visible to the naked eye and others microscopic, are present in many gems. Some add great beauty and interest to a gemstone, but they can also cause problems if a gemstone is cleaning in an inappropriate manner. “Lodolite” (Quartz with inclusions) by Mario Cateb is licensed under CC By 2.0

A professional gemologist who understands the “internal personalities” of your gems can help you select the appropriate mechanical gemstone cleaning method.

The Risk Factors Hidden In Some Popular Gems

Emerald is a green colored beryl, normally a rather hardy mineral. However, heavy inclusions in an emerald can weaken the mineral’s structure. The stresses of a mechanical cleaning could ruin, or even shatter, an emerald.

A topaz can appear perfectly flawless, even under magnification. However, in order to achieve the best jewelry presentation for these gems, jewelers often have to press the prong settings directly against a topaz’s cleavage plane, an internal plane along which the gemstone has a natural tendency to break. If a prong is exerting undue pressure on that plane, vibrations and even sudden temperature changes could split a topaz as neatly as a slice of bread.

Although a diamond may not cleave a readily as a topaz, the same danger lurks within it. There have been incidents where one lovely diamond went into a mechanical cleaning system, but two or three smaller diamonds came out. Recent research indicates some of these accidents may be due to unseen liquid inclusions. The high temperatures created by some mechanical systems may cause the liquids to heat, then expand, and then … Crack!

How do mechanical gemstone cleaning systems work? Here are brief descriptions of the three major systems and some caveats.

Ultrasonic Cleaning

Ultrasonic units usually consist of a stainless steel tank with millions of microscopic frequency waves bouncing around in a special liquid. The implosions (inward collapse) of the bubbles against a piece of jewelry placed inside the tank function as tiny vacuums that siphon off dirt and grime.

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Ultrasonic units have many household uses, but know your gemstones and read about the ultrasonic cleaning system before you immerse your jewelry in one. “DSCF6331” by Emmanuel Gilloz is licensed under CC By-SA 2.0

The frequency impulses concentrate on the hardest element in the liquid. When you have a diamond in the bath you may imagine where all the energy is focused. Should the diamond, or any other gemstone, have an incipient cleave or pressure point the energy could aggravate the weakness to the point of destruction.

Some gemstones, such as emeralds, rubies, and sapphires, are oil treated to enhance their color and transparency. The tiny bubbles in ultrasonic cleaning can drive out the oil, resulting in some very sad, sorry versions of your prized treasures in need of another oil treatment.

You would be well advised to never submit opal, pearl, emerald, tanzanite, coral, turquoise, malachite, and amber to ultrasonic cleaning. Unless a gemologist can assure you that your rubies or sapphires have never been oiled, keep these gems out of an ultrasonic tank, too.

If you have your heart set on doing some ultrasonic cleaning at home, you can find a variety of units on Amazon or eBay. Here are some tips for using your cleaner:

  • Don’t let the jewelry piece lay on the bottom of the stainless steel tank. Keep it suspended so it floats in the liquid without touching the tank.
  • Check the temperature of the liquid. Prolonged use of an ultrasonic cleaner can run the temperature of the bath up to unsafe levels, exposing your gems to thermal shock and causing a liquid filled inclusion to literally blow the gem apart.
  • Check the stones in your jewelry item before and after cleaning. The vibrations can dislodge a loose stone so that it falls to the bottom of the tank.
  • Use commercially prepared cleaning solutions intended for use in an ultrasonic cleaner.

Steam Cleaning and Boiling

Not too many consumers have a steam cleaner. Although they’re more efficient for large scale cleaning tasks, they create some thermal dangers by elevating the temperature of a gemstone quickly then rapidly returning it to a normal temperature. Nonetheless, steam is highly efficient for melting grease and oil and blowing it away with other dirt. Fortunately, a quick squirt of high temperature steam is about all the average cleaning job requires.

Of the three major mechanical cleaning systems, boiling is the one most used by non-professionals. (Professionals often use it, too). It’s simple and can be done quickly, but it’s not without risk.  Essentially, the boiling method is much like the warm water, mild detergent, and soft brush method, but at a much higher temperature. Both jewelry and detergent are placed in a pot of water and brought to a boil. After a period of time, the pieces are removed, scrubbed with a soft brush, rinsed, and dried.

Just keep in mind that even a diamond can be ruined if the water boils off completely and it’s left sitting in a hot pot.

The extreme temperatures and rapid changes that occur in steam cleaning and boiling are risky because some gemstones have inclusions that may actually be entirely different minerals. The two could have different heating coefficients, and a rapid fluctuation in the host gem’s temperature could produce stresses that cause a split. Liquid inclusions, of course, can also create structural pressure if heated.

If ever you intend to expose one of your gems to high heat, prepare the gem first. Pre-warm it by immersing it in warm and then warmer water. (All three mechanical cleaning techniques have the potential to elevate a stone’s temperature too quickly).  If you make it to a high temperature safely, realize that coming back down again poses an equal challenge. Cool it down this time by placing it in warm water. Avoid exposing a gem you’ve just heated to cold air.

The Bottom Line

Even if you want to leave the mechanical gemstone cleaning to the professionals, ask them questions about their procedures and your gemstones. If their answers don’t satisfy you, go elsewhere. A little knowledge of gems, their care requirements, and different cleaning systems will help you make the best possible choice.

Gemstone Care Series

How To Clean Your Gemstone Jewelry

Mechanical Gemstone Cleaning

Gemstone Care Guide

Care Guide For Pearls and Opals